This invention relates generally to diazotype reproduction apparatus, and more particularly, to an improved wick-type applicator for feeding a supply of liquid to the applicator roller of the developer section of such a reproduction apparatus.
The reproduction apparatus involved in this invention is of the type that requires a controlled amount of liquid developing agent to be applied to the light-sensitive diazotype material. Such reproduction apparatus comprises a special applicator roller having a surface finish adapted to carry such controlled amounts of liquid thereon. The usual construction of such an apparatus requires the latent image-bearing diazotype material to be pressed against the roller surface thereby transferring the controlled amount of liquid in order to develop the azo dye image thereon. The metering of liquid is achieved by the use of a wiper blade for removing excess developing liquid from the surface of the roller, and a pressure device for pressing the sheet of paper against the roller to pick up the precise amount of fluid. While a wide range of constructions may be used for pressing the sheet against the applicator roller, one of the preferred techniques is the use of a pressure blade similar to the wiper blade.
One of the important aspects of the construction of such a developer device is the liquid supply system which applies an excess amount of liquid to the developer roller surface which ultimately is metered by the aforementioned wiper blade. The means known up to the present time for supplying such a developer liquid involved pumping the liquid from a reservoir to a manifold dispensing tube running parallel to the roller, and then collecting all excess liquid which flowed off the roller after passing through the metering step. Hence, a rather complex liquid channel and feed system was required. Such delivery systems which require the use of a pump are complicated to fabricate, and increase the cost of the equipment.
Another technique for applying the liquid to the surface of the roller is by partial immersion of a roller in a trough containing the liquid. Immersion systems suffer from the problem of exposing the liquid to the atmosphere and to contamination and evaporation. The immersion systems additionally suffer from the disadvantage of having to impart larger volumes of the developer liquid into the system and, hence, detract from the economics of the reproduction process.
The use of a material formed into an applicator wick soaked with the developer liquid has been known, but such wick constructions suffer from the deficiency of non-uniform delivery because of their particular fibrous structure and have been found to be rather fragile, giving up the fibrous materials of which they are made which become contaminants to the liquid and to the developing techniques by virtue of the fact that they become trapped in the metering devices and therefore cause uneven and streaked reproduction of the copies.